Absolutely and you really need to do that. You can have both categories and sub categories, etc. Write out the categories you need before starting or you can get confused, at least I did, when first setting them up. Currently I'm not up to giving directions on how to do so, but just go to categories which is the first option on your administration navigation bar on the left of your page.

Might I suggest getting rid of all the non-descriptive text on your listings. It is considered boilerplate and Google doesn't like to see it. Especially as ebay imported everything in one huge almost unreadable paragraph which makes it hard to read.